001/**
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.activemq.broker.region;
018
019import java.io.IOException;
020import java.util.ArrayList;
021import java.util.LinkedList;
022import java.util.List;
023import java.util.concurrent.atomic.AtomicLong;
024
025import javax.jms.JMSException;
026
027import org.apache.activemq.ActiveMQMessageAudit;
028import org.apache.activemq.broker.Broker;
029import org.apache.activemq.broker.ConnectionContext;
030import org.apache.activemq.broker.region.cursors.FilePendingMessageCursor;
031import org.apache.activemq.broker.region.cursors.PendingMessageCursor;
032import org.apache.activemq.broker.region.cursors.VMPendingMessageCursor;
033import org.apache.activemq.broker.region.policy.MessageEvictionStrategy;
034import org.apache.activemq.broker.region.policy.OldestMessageEvictionStrategy;
035import org.apache.activemq.command.ConsumerControl;
036import org.apache.activemq.command.ConsumerInfo;
037import org.apache.activemq.command.Message;
038import org.apache.activemq.command.MessageAck;
039import org.apache.activemq.command.MessageDispatch;
040import org.apache.activemq.command.MessageDispatchNotification;
041import org.apache.activemq.command.MessageId;
042import org.apache.activemq.command.MessagePull;
043import org.apache.activemq.command.Response;
044import org.apache.activemq.thread.Scheduler;
045import org.apache.activemq.transaction.Synchronization;
046import org.apache.activemq.transport.TransmitCallback;
047import org.apache.activemq.usage.SystemUsage;
048import org.slf4j.Logger;
049import org.slf4j.LoggerFactory;
050
051public class TopicSubscription extends AbstractSubscription {
052
053    private static final Logger LOG = LoggerFactory.getLogger(TopicSubscription.class);
054    private static final AtomicLong CURSOR_NAME_COUNTER = new AtomicLong(0);
055
056    protected PendingMessageCursor matched;
057    protected final SystemUsage usageManager;
058    boolean singleDestination = true;
059    Destination destination;
060    private final Scheduler scheduler;
061
062    private int maximumPendingMessages = -1;
063    private MessageEvictionStrategy messageEvictionStrategy = new OldestMessageEvictionStrategy();
064    private int discarded;
065    private final Object matchedListMutex = new Object();
066    private int memoryUsageHighWaterMark = 95;
067    // allow duplicate suppression in a ring network of brokers
068    protected int maxProducersToAudit = 1024;
069    protected int maxAuditDepth = 1000;
070    protected boolean enableAudit = false;
071    protected ActiveMQMessageAudit audit;
072    protected boolean active = false;
073    protected boolean discarding = false;
074
075    //Used for inflight message size calculations
076    protected final Object dispatchLock = new Object();
077    protected final List<MessageReference> dispatched = new ArrayList<MessageReference>();
078
079    public TopicSubscription(Broker broker,ConnectionContext context, ConsumerInfo info, SystemUsage usageManager) throws Exception {
080        super(broker, context, info);
081        this.usageManager = usageManager;
082        String matchedName = "TopicSubscription:" + CURSOR_NAME_COUNTER.getAndIncrement() + "[" + info.getConsumerId().toString() + "]";
083        if (info.getDestination().isTemporary() || broker.getTempDataStore()==null ) {
084            this.matched = new VMPendingMessageCursor(false);
085        } else {
086            this.matched = new FilePendingMessageCursor(broker,matchedName,false);
087        }
088
089        this.scheduler = broker.getScheduler();
090    }
091
092    public void init() throws Exception {
093        this.matched.setSystemUsage(usageManager);
094        this.matched.setMemoryUsageHighWaterMark(getCursorMemoryHighWaterMark());
095        this.matched.start();
096        if (enableAudit) {
097            audit= new ActiveMQMessageAudit(maxAuditDepth, maxProducersToAudit);
098        }
099        this.active=true;
100    }
101
102    @Override
103    public void add(MessageReference node) throws Exception {
104        if (isDuplicate(node)) {
105            return;
106        }
107        // Lets use an indirect reference so that we can associate a unique
108        // locator /w the message.
109        node = new IndirectMessageReference(node.getMessage());
110        getSubscriptionStatistics().getEnqueues().increment();
111        synchronized (matchedListMutex) {
112            // if this subscriber is already discarding a message, we don't want to add
113            // any more messages to it as those messages can only be advisories generated in the process,
114            // which can trigger the recursive call loop
115            if (discarding) return;
116
117            if (!isFull() && matched.isEmpty()) {
118                // if maximumPendingMessages is set we will only discard messages which
119                // have not been dispatched (i.e. we allow the prefetch buffer to be filled)
120                dispatch(node);
121                setSlowConsumer(false);
122            } else {
123                if (info.getPrefetchSize() > 1 && matched.size() > info.getPrefetchSize()) {
124                    // Slow consumers should log and set their state as such.
125                    if (!isSlowConsumer()) {
126                        LOG.warn("{}: has twice its prefetch limit pending, without an ack; it appears to be slow", toString());
127                        setSlowConsumer(true);
128                        for (Destination dest: destinations) {
129                            dest.slowConsumer(getContext(), this);
130                        }
131                    }
132                }
133                if (maximumPendingMessages != 0) {
134                    boolean warnedAboutWait = false;
135                    while (active) {
136                        while (matched.isFull()) {
137                            if (getContext().getStopping().get()) {
138                                LOG.warn("{}: stopped waiting for space in pendingMessage cursor for: {}", toString(), node.getMessageId());
139                                getSubscriptionStatistics().getEnqueues().decrement();
140                                return;
141                            }
142                            if (!warnedAboutWait) {
143                                LOG.info("{}: Pending message cursor [{}] is full, temp usag ({}%) or memory usage ({}%) limit reached, blocking message add() pending the release of resources.",
144                                        new Object[]{
145                                                toString(),
146                                                matched,
147                                                matched.getSystemUsage().getTempUsage().getPercentUsage(),
148                                                matched.getSystemUsage().getMemoryUsage().getPercentUsage()
149                                        });
150                                warnedAboutWait = true;
151                            }
152                            matchedListMutex.wait(20);
153                        }
154                        // Temporary storage could be full - so just try to add the message
155                        // see https://issues.apache.org/activemq/browse/AMQ-2475
156                        if (matched.tryAddMessageLast(node, 10)) {
157                            break;
158                        }
159                    }
160                    if (maximumPendingMessages > 0) {
161                        // calculate the high water mark from which point we
162                        // will eagerly evict expired messages
163                        int max = messageEvictionStrategy.getEvictExpiredMessagesHighWatermark();
164                        if (maximumPendingMessages > 0 && maximumPendingMessages < max) {
165                            max = maximumPendingMessages;
166                        }
167                        if (!matched.isEmpty() && matched.size() > max) {
168                            removeExpiredMessages();
169                        }
170                        // lets discard old messages as we are a slow consumer
171                        while (!matched.isEmpty() && matched.size() > maximumPendingMessages) {
172                            int pageInSize = matched.size() - maximumPendingMessages;
173                            // only page in a 1000 at a time - else we could blow the memory
174                            pageInSize = Math.max(1000, pageInSize);
175                            LinkedList<MessageReference> list = null;
176                            MessageReference[] oldMessages=null;
177                            synchronized(matched){
178                                list = matched.pageInList(pageInSize);
179                                oldMessages = messageEvictionStrategy.evictMessages(list);
180                                for (MessageReference ref : list) {
181                                    ref.decrementReferenceCount();
182                                }
183                            }
184                            int messagesToEvict = 0;
185                            if (oldMessages != null){
186                                messagesToEvict = oldMessages.length;
187                                for (int i = 0; i < messagesToEvict; i++) {
188                                    MessageReference oldMessage = oldMessages[i];
189                                    discard(oldMessage);
190                                }
191                            }
192                            // lets avoid an infinite loop if we are given a bad eviction strategy
193                            // for a bad strategy lets just not evict
194                            if (messagesToEvict == 0) {
195                                LOG.warn("No messages to evict returned for {} from eviction strategy: {} out of {} candidates", new Object[]{
196                                        destination, messageEvictionStrategy, list.size()
197                                });
198                                break;
199                            }
200                        }
201                    }
202                    dispatchMatched();
203                }
204            }
205        }
206    }
207
208    private boolean isDuplicate(MessageReference node) {
209        boolean duplicate = false;
210        if (enableAudit && audit != null) {
211            duplicate = audit.isDuplicate(node);
212            if (LOG.isDebugEnabled()) {
213                if (duplicate) {
214                    LOG.debug("{}, ignoring duplicate add: {}", this, node.getMessageId());
215                }
216            }
217        }
218        return duplicate;
219    }
220
221    /**
222     * Discard any expired messages from the matched list. Called from a
223     * synchronized block.
224     *
225     * @throws IOException
226     */
227    protected void removeExpiredMessages() throws IOException {
228        try {
229            matched.reset();
230            while (matched.hasNext()) {
231                MessageReference node = matched.next();
232                node.decrementReferenceCount();
233                if (node.isExpired()) {
234                    matched.remove();
235                    node.decrementReferenceCount();
236                    if (broker.isExpired(node)) {
237                        ((Destination) node.getRegionDestination()).getDestinationStatistics().getExpired().increment();
238                        broker.messageExpired(getContext(), node, this);
239                    }
240                    break;
241                }
242            }
243        } finally {
244            matched.release();
245        }
246    }
247
248    @Override
249    public void processMessageDispatchNotification(MessageDispatchNotification mdn) {
250        synchronized (matchedListMutex) {
251            try {
252                matched.reset();
253                while (matched.hasNext()) {
254                    MessageReference node = matched.next();
255                    node.decrementReferenceCount();
256                    if (node.getMessageId().equals(mdn.getMessageId())) {
257                        synchronized(dispatchLock) {
258                            matched.remove();
259                            getSubscriptionStatistics().getDispatched().increment();
260                            dispatched.add(node);
261                            getSubscriptionStatistics().getInflightMessageSize().addSize(node.getSize());
262                            node.decrementReferenceCount();
263                        }
264                        break;
265                    }
266                }
267            } finally {
268                matched.release();
269            }
270        }
271    }
272
273    @Override
274    public synchronized void acknowledge(final ConnectionContext context, final MessageAck ack) throws Exception {
275        super.acknowledge(context, ack);
276
277        if (ack.isStandardAck()) {
278            updateStatsOnAck(context, ack);
279        } else if (ack.isPoisonAck()) {
280            if (ack.isInTransaction()) {
281                throw new JMSException("Poison ack cannot be transacted: " + ack);
282            }
283            updateStatsOnAck(context, ack);
284            if (getPrefetchSize() != 0) {
285                decrementPrefetchExtension(ack.getMessageCount());
286            }
287        } else if (ack.isIndividualAck()) {
288            updateStatsOnAck(context, ack);
289            if (getPrefetchSize() != 0 && ack.isInTransaction()) {
290                incrementPrefetchExtension(ack.getMessageCount());
291            }
292        } else if (ack.isExpiredAck()) {
293            updateStatsOnAck(ack);
294            if (getPrefetchSize() != 0) {
295                incrementPrefetchExtension(ack.getMessageCount());
296            }
297        } else if (ack.isDeliveredAck()) {
298            // Message was delivered but not acknowledged: update pre-fetch counters.
299            if (getPrefetchSize() != 0) {
300                incrementPrefetchExtension(ack.getMessageCount());
301            }
302        } else if (ack.isRedeliveredAck()) {
303            // No processing for redelivered needed
304            return;
305        } else {
306            throw new JMSException("Invalid acknowledgment: " + ack);
307        }
308
309        dispatchMatched();
310    }
311
312    private void updateStatsOnAck(final ConnectionContext context, final MessageAck ack) {
313        if (context.isInTransaction()) {
314            context.getTransaction().addSynchronization(new Synchronization() {
315
316                @Override
317                public void beforeEnd() {
318                    if (getPrefetchSize() != 0) {
319                        decrementPrefetchExtension(ack.getMessageCount());
320                    }
321                }
322
323                @Override
324                public void afterCommit() throws Exception {
325                    updateStatsOnAck(ack);
326                    dispatchMatched();
327                }
328            });
329        } else {
330            updateStatsOnAck(ack);
331        }
332    }
333
334    @Override
335    public Response pullMessage(ConnectionContext context, final MessagePull pull) throws Exception {
336
337        // The slave should not deliver pull messages.
338        if (getPrefetchSize() == 0) {
339
340            final long currentDispatchedCount = getSubscriptionStatistics().getDispatched().getCount();
341            prefetchExtension.set(pull.getQuantity());
342            dispatchMatched();
343
344            // If there was nothing dispatched.. we may need to setup a timeout.
345            if (currentDispatchedCount == getSubscriptionStatistics().getDispatched().getCount() || pull.isAlwaysSignalDone()) {
346
347                // immediate timeout used by receiveNoWait()
348                if (pull.getTimeout() == -1) {
349                    // Send a NULL message to signal nothing pending.
350                    dispatch(null);
351                    prefetchExtension.set(0);
352                }
353
354                if (pull.getTimeout() > 0) {
355                    scheduler.executeAfterDelay(new Runnable() {
356
357                        @Override
358                        public void run() {
359                            pullTimeout(currentDispatchedCount, pull.isAlwaysSignalDone());
360                        }
361                    }, pull.getTimeout());
362                }
363            }
364        }
365        return null;
366    }
367
368    /**
369     * Occurs when a pull times out. If nothing has been dispatched since the
370     * timeout was setup, then send the NULL message.
371     */
372    private final void pullTimeout(long currentDispatchedCount, boolean alwaysSendDone) {
373        synchronized (matchedListMutex) {
374            if (currentDispatchedCount == getSubscriptionStatistics().getDispatched().getCount() || alwaysSendDone) {
375                try {
376                    dispatch(null);
377                } catch (Exception e) {
378                    context.getConnection().serviceException(e);
379                } finally {
380                    prefetchExtension.set(0);
381                }
382            }
383        }
384    }
385
386    /**
387     * Update the statistics on message ack.
388     * @param ack
389     */
390    private void updateStatsOnAck(final MessageAck ack) {
391        synchronized(dispatchLock) {
392            boolean inAckRange = false;
393            List<MessageReference> removeList = new ArrayList<MessageReference>();
394            for (final MessageReference node : dispatched) {
395                MessageId messageId = node.getMessageId();
396                if (ack.getFirstMessageId() == null
397                        || ack.getFirstMessageId().equals(messageId)) {
398                    inAckRange = true;
399                }
400                if (inAckRange) {
401                    removeList.add(node);
402                    if (ack.getLastMessageId().equals(messageId)) {
403                        break;
404                    }
405                }
406            }
407
408            for (final MessageReference node : removeList) {
409                dispatched.remove(node);
410                getSubscriptionStatistics().getInflightMessageSize().addSize(-node.getSize());
411                getSubscriptionStatistics().getDequeues().increment();
412                ((Destination)node.getRegionDestination()).getDestinationStatistics().getDequeues().increment();
413                ((Destination)node.getRegionDestination()).getDestinationStatistics().getInflight().decrement();
414                if (info.isNetworkSubscription()) {
415                    ((Destination)node.getRegionDestination()).getDestinationStatistics().getForwards().add(ack.getMessageCount());
416                }
417                if (ack.isExpiredAck()) {
418                    destination.getDestinationStatistics().getExpired().add(ack.getMessageCount());
419                }
420            }
421        }
422    }
423
424    private void incrementPrefetchExtension(int amount) {
425        while (true) {
426            int currentExtension = prefetchExtension.get();
427            int newExtension = Math.max(0, currentExtension + amount);
428            if (prefetchExtension.compareAndSet(currentExtension, newExtension)) {
429                break;
430            }
431        }
432    }
433
434    private void decrementPrefetchExtension(int amount) {
435        while (true) {
436            int currentExtension = prefetchExtension.get();
437            int newExtension = Math.max(0, currentExtension - amount);
438            if (prefetchExtension.compareAndSet(currentExtension, newExtension)) {
439                break;
440            }
441        }
442    }
443
444    @Override
445    public int countBeforeFull() {
446        return getPrefetchSize() == 0 ? prefetchExtension.get() : info.getPrefetchSize() + prefetchExtension.get() - getDispatchedQueueSize();
447    }
448
449    @Override
450    public int getPendingQueueSize() {
451        return matched();
452    }
453
454    @Override
455    public long getPendingMessageSize() {
456        synchronized (matchedListMutex) {
457            return matched.messageSize();
458        }
459    }
460
461    @Override
462    public int getDispatchedQueueSize() {
463        return (int)(getSubscriptionStatistics().getDispatched().getCount() -
464                     getSubscriptionStatistics().getDequeues().getCount());
465    }
466
467    public int getMaximumPendingMessages() {
468        return maximumPendingMessages;
469    }
470
471    @Override
472    public long getDispatchedCounter() {
473        return getSubscriptionStatistics().getDispatched().getCount();
474    }
475
476    @Override
477    public long getEnqueueCounter() {
478        return getSubscriptionStatistics().getEnqueues().getCount();
479    }
480
481    @Override
482    public long getDequeueCounter() {
483        return getSubscriptionStatistics().getDequeues().getCount();
484    }
485
486    /**
487     * @return the number of messages discarded due to being a slow consumer
488     */
489    public int discarded() {
490        synchronized (matchedListMutex) {
491            return discarded;
492        }
493    }
494
495    /**
496     * @return the number of matched messages (messages targeted for the
497     *         subscription but not yet able to be dispatched due to the
498     *         prefetch buffer being full).
499     */
500    public int matched() {
501        synchronized (matchedListMutex) {
502            return matched.size();
503        }
504    }
505
506    /**
507     * Sets the maximum number of pending messages that can be matched against
508     * this consumer before old messages are discarded.
509     */
510    public void setMaximumPendingMessages(int maximumPendingMessages) {
511        this.maximumPendingMessages = maximumPendingMessages;
512    }
513
514    public MessageEvictionStrategy getMessageEvictionStrategy() {
515        return messageEvictionStrategy;
516    }
517
518    /**
519     * Sets the eviction strategy used to decide which message to evict when the
520     * slow consumer needs to discard messages
521     */
522    public void setMessageEvictionStrategy(MessageEvictionStrategy messageEvictionStrategy) {
523        this.messageEvictionStrategy = messageEvictionStrategy;
524    }
525
526    public int getMaxProducersToAudit() {
527        return maxProducersToAudit;
528    }
529
530    public synchronized void setMaxProducersToAudit(int maxProducersToAudit) {
531        this.maxProducersToAudit = maxProducersToAudit;
532        if (audit != null) {
533            audit.setMaximumNumberOfProducersToTrack(maxProducersToAudit);
534        }
535    }
536
537    public int getMaxAuditDepth() {
538        return maxAuditDepth;
539    }
540
541    public synchronized void setMaxAuditDepth(int maxAuditDepth) {
542        this.maxAuditDepth = maxAuditDepth;
543        if (audit != null) {
544            audit.setAuditDepth(maxAuditDepth);
545        }
546    }
547
548    public boolean isEnableAudit() {
549        return enableAudit;
550    }
551
552    public synchronized void setEnableAudit(boolean enableAudit) {
553        this.enableAudit = enableAudit;
554        if (enableAudit && audit == null) {
555            audit = new ActiveMQMessageAudit(maxAuditDepth,maxProducersToAudit);
556        }
557    }
558
559    // Implementation methods
560    // -------------------------------------------------------------------------
561    @Override
562    public boolean isFull() {
563        return getPrefetchSize() == 0 ? prefetchExtension.get() == 0 : getDispatchedQueueSize() - prefetchExtension.get() >= info.getPrefetchSize();
564    }
565
566    @Override
567    public int getInFlightSize() {
568        return getDispatchedQueueSize();
569    }
570
571    /**
572     * @return true when 60% or more room is left for dispatching messages
573     */
574    @Override
575    public boolean isLowWaterMark() {
576        return (getDispatchedQueueSize() - prefetchExtension.get()) <= (info.getPrefetchSize() * .4);
577    }
578
579    /**
580     * @return true when 10% or less room is left for dispatching messages
581     */
582    @Override
583    public boolean isHighWaterMark() {
584        return (getDispatchedQueueSize() - prefetchExtension.get()) >= (info.getPrefetchSize() * .9);
585    }
586
587    /**
588     * @param memoryUsageHighWaterMark the memoryUsageHighWaterMark to set
589     */
590    public void setMemoryUsageHighWaterMark(int memoryUsageHighWaterMark) {
591        this.memoryUsageHighWaterMark = memoryUsageHighWaterMark;
592    }
593
594    /**
595     * @return the memoryUsageHighWaterMark
596     */
597    public int getMemoryUsageHighWaterMark() {
598        return this.memoryUsageHighWaterMark;
599    }
600
601    /**
602     * @return the usageManager
603     */
604    public SystemUsage getUsageManager() {
605        return this.usageManager;
606    }
607
608    /**
609     * @return the matched
610     */
611    public PendingMessageCursor getMatched() {
612        return this.matched;
613    }
614
615    /**
616     * @param matched the matched to set
617     */
618    public void setMatched(PendingMessageCursor matched) {
619        this.matched = matched;
620    }
621
622    /**
623     * inform the MessageConsumer on the client to change it's prefetch
624     *
625     * @param newPrefetch
626     */
627    @Override
628    public void updateConsumerPrefetch(int newPrefetch) {
629        if (context != null && context.getConnection() != null && context.getConnection().isManageable()) {
630            ConsumerControl cc = new ConsumerControl();
631            cc.setConsumerId(info.getConsumerId());
632            cc.setPrefetch(newPrefetch);
633            context.getConnection().dispatchAsync(cc);
634        }
635    }
636
637    private void dispatchMatched() throws IOException {
638        synchronized (matchedListMutex) {
639            if (!matched.isEmpty() && !isFull()) {
640                try {
641                    matched.reset();
642
643                    while (matched.hasNext() && !isFull()) {
644                        MessageReference message = matched.next();
645                        message.decrementReferenceCount();
646                        matched.remove();
647                        // Message may have been sitting in the matched list a while
648                        // waiting for the consumer to ak the message.
649                        if (message.isExpired()) {
650                            discard(message);
651                            continue; // just drop it.
652                        }
653                        dispatch(message);
654                    }
655                } finally {
656                    matched.release();
657                }
658            }
659        }
660    }
661
662    private void dispatch(final MessageReference node) throws IOException {
663        Message message = node != null ? node.getMessage() : null;
664        if (node != null) {
665            node.incrementReferenceCount();
666        }
667        // Make sure we can dispatch a message.
668        MessageDispatch md = new MessageDispatch();
669        md.setMessage(message);
670        md.setConsumerId(info.getConsumerId());
671        if (node != null) {
672            md.setDestination(((Destination)node.getRegionDestination()).getActiveMQDestination());
673            synchronized(dispatchLock) {
674                getSubscriptionStatistics().getDispatched().increment();
675                dispatched.add(node);
676                getSubscriptionStatistics().getInflightMessageSize().addSize(node.getSize());
677            }
678
679            // Keep track if this subscription is receiving messages from a single destination.
680            if (singleDestination) {
681                if (destination == null) {
682                    destination = (Destination)node.getRegionDestination();
683                } else {
684                    if (destination != node.getRegionDestination()) {
685                        singleDestination = false;
686                    }
687                }
688            }
689
690            if (getPrefetchSize() == 0) {
691                decrementPrefetchExtension(1);
692            }
693        }
694
695        if (info.isDispatchAsync()) {
696            if (node != null) {
697                md.setTransmitCallback(new TransmitCallback() {
698
699                    @Override
700                    public void onSuccess() {
701                        Destination regionDestination = (Destination) node.getRegionDestination();
702                        regionDestination.getDestinationStatistics().getDispatched().increment();
703                        regionDestination.getDestinationStatistics().getInflight().increment();
704                        node.decrementReferenceCount();
705                    }
706
707                    @Override
708                    public void onFailure() {
709                        Destination regionDestination = (Destination) node.getRegionDestination();
710                        regionDestination.getDestinationStatistics().getDispatched().increment();
711                        regionDestination.getDestinationStatistics().getInflight().increment();
712                        node.decrementReferenceCount();
713                    }
714                });
715            }
716            context.getConnection().dispatchAsync(md);
717        } else {
718            context.getConnection().dispatchSync(md);
719            if (node != null) {
720                Destination regionDestination = (Destination) node.getRegionDestination();
721                regionDestination.getDestinationStatistics().getDispatched().increment();
722                regionDestination.getDestinationStatistics().getInflight().increment();
723                node.decrementReferenceCount();
724            }
725        }
726    }
727
728    private void discard(MessageReference message) {
729        discarding = true;
730        try {
731            message.decrementReferenceCount();
732            matched.remove(message);
733            discarded++;
734            if (destination != null) {
735                destination.getDestinationStatistics().getDequeues().increment();
736            }
737            LOG.debug("{}, discarding message {}", this, message);
738            Destination dest = (Destination) message.getRegionDestination();
739            if (dest != null) {
740                dest.messageDiscarded(getContext(), this, message);
741            }
742            broker.getRoot().sendToDeadLetterQueue(getContext(), message, this, new Throwable("TopicSubDiscard. ID:" + info.getConsumerId()));
743        } finally {
744            discarding = false;
745        }
746    }
747
748    @Override
749    public String toString() {
750        return "TopicSubscription:" + " consumer=" + info.getConsumerId() + ", destinations=" + destinations.size() + ", dispatched=" + getDispatchedQueueSize() + ", delivered="
751                + getDequeueCounter() + ", matched=" + matched() + ", discarded=" + discarded() + ", prefetchExtension=" + prefetchExtension.get();
752    }
753
754    @Override
755    public void destroy() {
756        this.active=false;
757        synchronized (matchedListMutex) {
758            try {
759                matched.destroy();
760            } catch (Exception e) {
761                LOG.warn("Failed to destroy cursor", e);
762            }
763        }
764        setSlowConsumer(false);
765        synchronized(dispatchLock) {
766            dispatched.clear();
767        }
768    }
769
770    @Override
771    public int getPrefetchSize() {
772        return info.getPrefetchSize();
773    }
774
775    @Override
776    public void setPrefetchSize(int newSize) {
777        info.setPrefetchSize(newSize);
778        try {
779            dispatchMatched();
780        } catch(Exception e) {
781            LOG.trace("Caught exception on dispatch after prefetch size change.");
782        }
783    }
784}